%/**
%Focus-vector computation
%@param alpha - elevation, scalar, rad
%@param beta - azimuth, scalar, rad
%@return H - focus-vector
% relevant to antenna's center, 4x1, rad
%*/
function Hv = H( alpha, beta ) 
 k = [cos(alpha)*cos(beta); % Unit vector
 cos(alpha)*sin(beta);
 sin(alpha)];
 r{1} = [1/4 0 0]; % Antenna's radius-vector, lambdas
 r{2} = [-1/4 0 0];

 phi = nan(2,1);
 for i = 1:2
 phi(i) = 2*pi * r{i} * k;
 end

 Hv = exp( 1i * phi );
end 
